By the action of dehydrating agents they are converted into aldehydes or ketones.
In the presence of a dehydrating agent (such as acetic anhydride), it combines with aldehydes to form compounds of the type R CH: C(COOH) 2, or their decomposition products (formed by loss of C02) R CH: CH COOH.
The aldoximes are converted by the action of dehydrating agents into nitriles: RCH: NOH-->R C: N+H 2 0.
This water cannot be entirely removed by fractional distillation, and to prepare anhydrous or "absolute" alcohol the commercial product must be allowed to stand over some dehydrating agent, such as caustic lime, baryta, anhydrous copper sulphate, &c., and then distilled.
The olefines may be synthetically prepared by eliminating water from the alcohols of the general formula CnH2n+1 OH, using sulphuric acid or zinc chloride generally as the dehydrating agent, although phosphorus pentoxide, syrupy phosphoric acid and anhydrous oxalic acid may frequently be substituted.